NGK Iridium IX Spark Plugs
Long-life iridium plugs from a leading OE supplier — a reliable, widely fitting choice to restore strong spark and clear misfires.
- Long-life iridium
- OE-quality, wide fitment
- Consistent spark
Engine Repair Parts
Best Spark Plugs & Ignition Coils to Fix a Misfire
The short answer
The best fix for a misfire code (P0300–P0312) usually starts with a fresh set of iridium spark plugs in the manufacturer-specified heat range, plus replacing any weak ignition coil — together they restore strong, consistent spark and clear the most common cause of a flashing check engine light.
Misfire codes (P0300 random, P0301–P0312 cylinder-specific) and a flashing check engine light most often trace to worn spark plugs or a failing ignition coil. Replacing plugs at the recommended interval and swapping a bad coil restores spark and protects your catalytic converter. Always use the plug type and gap your engine calls for.
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Our top pick, best spark plugs
NGK Iridium IX Spark Plugs
Quick picks at a glance
- Best spark plugs NGK Iridium IX Spark Plugs Check price
- Best alternative plugs Denso Iridium Power Spark Plugs Check price
- Best ignition coil ACDelco / Motorcraft Ignition Coil Check price
What to look for
- Correct part number — match plugs and coils to your exact year/make/model/engine.
- Plug material — iridium and platinum plugs last far longer than copper; use what your engine specifies.
- Pre-gapped plugs set to spec (verify the gap before installing).
- OE-quality coils — a flashing CEL with a cylinder-specific misfire often means that coil is failing.
- Buy plugs as a full set; replace coils individually or as a set if several are aging.
Our picks
Denso Iridium Power Spark Plugs
Another top-tier iridium plug with excellent fitment coverage — a strong alternative if Denso is the OE on your engine.
- Fine-wire iridium
- Strong fitment coverage
- Reliable ignition
ACDelco / Motorcraft Ignition Coil
OE-grade ignition coils that match many domestic engines — the part to replace when a cylinder-specific misfire points to a failing coil.
- OE-grade output
- Direct-fit options
- Fixes coil-related misfires
Frequently asked questions
Will new spark plugs fix a P0300 misfire code?
Often, yes — worn spark plugs are the most common cause of misfire codes. If a fresh set of the correct plugs does not clear it, the next suspects are a failing ignition coil, a fuel injector, or a vacuum leak. A cylinder-specific code (P0301–P0312) points to that exact cylinder.
How do I know if it is the spark plug or the ignition coil?
A cylinder-specific misfire that follows the coil when you swap it to another cylinder confirms the coil. If the misfire stays put after a coil swap, suspect the plug, injector, or compression on that cylinder. Replacing aging plugs as a set is the usual first step.
Why is my check engine light flashing with a misfire?
A flashing CEL means an active misfire is dumping raw fuel into the exhaust, which can quickly damage the catalytic converter. Reduce load and address it promptly — fresh plugs and a known-good coil are the most common fix.
Diagnose it first with AXLY.pro — free
AXLY.pro is a free iPhone app that pairs with any Bluetooth OBD2 adapter to read codes, watch live engine data, and time your runs — so you fix the right thing before you buy parts.
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Top pick: NGK Iridium IX Spark Plugs Check price